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Diffractive Catheter Enhances OCT Imaging

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A new imaging catheter that enables real-time, ultrahigh-resolution OCT imaging at 800 nm to form a 3-D volumetric dataset could potentially improve image contrast via increased light scattering and less tissue absorption.

Called a diffractive catheter, the device was developed by researchers from Johns Hopkins University and the University of Washington. Currently, such catheters and endoscopes are designed to work at around 1300 nm, but a smaller wavelength is more convenient in achieving an ultrahigh-axial resolution with a broadband light source.


Reflected spectra of the imaging catheters with and without a diffractive lens. Images courtesy of Optics Letters.

The instrument features a diffractive microlens to manage chromatic aberration. Because it was originally designed for longer wavelengths, it can only alleviate the aberration rather than remove it. With further investigation and optimization of the diffractive lens, better image quality can be accomplished.

In the current study, a fiber rotary joint coupled with a broadband Ti:sapphire laser brought the imaging catheter’s lateral resolution to 6.2 µm and the axial resolution to 3µm. This allowed for 3-D full-circumferential endoscopic OCT imaging, something previously not possible with traditional setups.


The instrument’s 3-D capabilities were tested using in vivo imaging.


Schematic of an ultrahigh-resolution OCT imaging catheter with a diffractive lens to alleviate chromatic aberration.

Fine structures, such as a thin layer of muscularis mucosae embedded between lamina propria and submucosa (muscles that are part of the gastrointestinal tract), were easily identified. Such structures have historically been difficult to distinguish in the 1300-nm wavelength.

The research was funded by a National Institutes of Health grant and will be published in Optics Letters.

For more information, visit: www.opticsinfobase.org.

Published: March 2014
Glossary
broadband
Indicating a capability to deal with a relatively wide spectral bandwidth.
chromatic aberration
Chromatic aberration is an optical phenomenon that occurs when different wavelengths (colors) of light are refracted by a lens or optical system, leading to a failure to focus all colors to the same convergence point. This results in colored fringes or halos around the edges of objects, reducing the overall image quality and sharpness. Key points about chromatic aberration include: Cause: Chromatic aberration arises because different colors of light have different refractive indices...
ti:sapphire laser
A Ti:sapphire laser is a type of solid-state laser that utilizes a titanium-doped sapphire crystal as the gain medium. The name Ti:sapphire comes from the combination of titanium (Ti) as the dopant and sapphire (Al2O3) as the host material. Ti:sapphire laser suppliers → This type of laser is known for its tunability across a broad range of wavelengths in the visible and near-infrared spectrum, typically from around 680 nanometers (deep red) to 1100 nanometers (near-infrared)....
wavelength
Electromagnetic energy is transmitted in the form of a sinusoidal wave. The wavelength is the physical distance covered by one cycle of this wave; it is inversely proportional to frequency.
3-DAmericasbroadbandchromatic aberrationdiffractiveendoscopesImagingin vivo imagingJohns Hopkins UniversitylensesMarylandmicrolensMicroscopyNational Institutes of HealthOCT imagingOpticsResearch & TechnologyTech PulseTest & MeasurementTi:sapphire laserUniversity of Washingtonwavelengthimaging catheterstate of Washingtonfiber rotary jointmuscularis mucosaelamina propriasubmucosaLasers

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